PPI Calculator
Calculate display pixel density and pixel pitch from resolution and diagonal screen size.
Pixel density
Assumes square pixels and the stated active display diagonal. 4K UHD means 3840 × 2160, not cinema DCI 4K. Operating-system scaling does not change physical PPI.
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How this calculator works
The diagonal pixel count is the hypotenuse formed by the horizontal and vertical pixel dimensions. Divide it by the physical diagonal in inches to obtain pixels per inch. Pixel pitch is the physical spacing between adjacent pixels: 25.4 millimetres divided by PPI. Higher density means smaller pixels at the same display size; it does not describe colour accuracy, refresh rate or the quality of an image source.
Formula
PPI = √(horizontal pixels² + vertical pixels²) ÷ diagonal inches. Pixel pitch in mm = 25.4 ÷ PPI.
Assumptions & limitations
Assumes square pixels and the stated active display diagonal. 4K UHD means 3840 × 2160, not cinema DCI 4K. Operating-system scaling does not change physical PPI.
Worked example
A 27-inch 2560 × 1440 display has √(2560² + 1440²) ÷ 27 ≈ 108.78554 PPI. Its pixel pitch is approximately 0.2334869 mm.
Our approach to calculations ↗Common questions
Does changing display scaling change PPI?
No. Scaling changes the size of interface elements in logical pixels; the physical pixel density stays the same.
Is PPI the same as mouse DPI?
No. Display PPI describes pixels per inch. Mouse CPI/DPI describes reported movement counts per inch.
How do I enter an ultrawide monitor?
Choose Custom and enter its actual horizontal and vertical pixel counts plus active diagonal size.